The present invention relates to improvements in baby or adult disposable diapers.
Recent proposals for developing disposable diapers have been centered on improved urine or bowel movement leakage protection in a crotch area, front and rear waist ends.
Improved diapers have leg gathers of dual structure which comprise an inner gather and an outer gather. A topsheet accordingly comprises two different functional areas. For example, FIG. 6 illustrates such construction. A liquid-permeable topsheet 11 is positioned in a central portion of a diaper and a hydrophobic topsheet 12 is positioned in each of the opposite side portions of the diaper. Each side portion includes a leg gather.
In an effort to improve leakage protection around front and rear ends, a leakage resistant material 13, 14, such as a film, a non-woven fabric and the like, is provided in those ends as shown in FIG. 7, in association with waist gathers. This however requires a more complicated manufacturing process, and does not provide a satisfactory solution.
A new approach has been proposed that attempts to simultaneously solve leakage problems at side, front and rear ends. See, for example, Kokai Patent Sho 61-41304 and Kokai Patent Hei 3-2057.
Such approach is directed to providing side barriers and end cap barrier structures by cutting out a central portion 15 of a hydrophobic topsheet 16, as shown in FIG. 8, to connect side portions and opposite end portions.
These proposals typically make reference to a diaper having a pocket structure.
Such diapers having a pocket structure are illustrated in FIGS. 9 through 11. A liquid-permeable topsheet 18 is interposed between a liquid-impermeable backsheet 17 and a hidrophobic hydrophobic topsheet 16 having an apertured central portion 15. An absorbent body 19 backsheet 17 and the liquid-permeable topsheet 18. A space indicated by a numeral 20 is a pocket portion.
Various problems still need to be solved in order to fully enjoy the unique features of such diaper having a pocket structure.
A first problem resides in its function. Since the hydrophobic topsheet is spaced from the absorbent body 19 to form the pocket space 20, any movement and weight of a wearer is directly applied to the hydrophobic topsheet having the apertured central portion while a diaper is worn by the wearer. This causes deformation in the hydrophobic topsheet. A conventional non-woven material however generally has a relatively lower strength in a cross-direction, CD, than in a machine direction, MD, so that it is unable to sustain such influences, with the result that material breakage, tearing, or a planar displacement of the apertured central portion 15 may occur. As such planar displacement increases, the apertured central portion 15 moves outside a target zone to which urine is discharged. This causes significant problems. In order to solve these problems, it has been recommended that a material having higher strength and dimensional stability- be employed. This however adds to material cost. In order to prevent the planar displacement of the apertured portion from the target zone, the apertured portion may be made larger to accommodate such displacement. Alternatively, a stretchable material may be employed to provide the hydrophobic topsheet with freedom to conform to the movement of the wearer. However as the aperture in the apertured portion is increased, the pocket structure becomes less advantageous. The use of an elastic material for the hydrophobic topsheet increases the material cost.
A second problem resides in the manufacturing process for the diaper. In order to form the pocket structure, it is required that the size of the hydrophobic topsheet be formed to correspond with the size of the wearer, prior to cutout of the aperture 15. Incomplete cutting undesirably leaves the hydrophobic nonwoven material at the central portion of the diaper. Such a defective diaper has no commercial value. Therefore, not only is a highly precise cutting operation required, an investment for installing such cutting equipment renders the process very expensive. Further, cutout nonwoven portions are not reusable and treated as waste so that an increased amount of material is disadvantageously required.
The present invention is directed to reduce the material waste of the hydrophobic topsheet material and further to enlarge the size of the apertured portion. The present invention is further directed to improve leakage protection and to increase strength around the periphery of the apertured portion by placing an elastic material around the apertured portion.
In accordance with the present invention, there is provided a diaper having a pocket structure wherein an absorbent body is interposed between a liquid-impermeable backsheet and an apertured hydrophobic topsheet to form front and rear waist end portions and side crotch portions of a diaper. The hydrophobic topsheet comprises two separate sheets each having a concave portion and convex portions. The two sheets are arranged to face each other so that respective convex portions thereof partially overlay each other at front and rear end portions of the diaper to form pocket portions. A concave edge portion of each sheet is folded over by a predetermined width to enclose an elastic member so that the folded-over portions that face each other define an apertured portion therebetween.